The present invention relates generally to clinching apparatuses and more particularly to a clinching punch and joint formed therewith.
It is known to use a punch and die to create a clinch joint between workpiece sheets. Such a device is disclosed in U.S. Pat. No. 5,177,861 entitled “Apparatus for Joining Sheet Material” which issued to Sawdon on Jan. 12, 1993, and is commonly owned with the present application. This patent is incorporated by reference herein. This prior device was a significant step in the industry but there is still room for further improvements.
Another clinching construction is disclosed in U.S. Pat. No. 5,727,302 entitled “Die and Punch for Forming a Joint and Method of Making the Die” which issued to Sawdon on Mar. 17, 1998, and is commonly owned with the present application. This is also incorporated by reference herein. This prior punch includes a 5° frusto-conical taper which was intended to advantageously prevent high stress concentrations and to improve the tool life during high pressure tool flexure misalignments.
In accordance with the present invention, a clinching apparatus includes a clinching punch having a specifically dimensioned tapered surface which improves the strength of a clinch joint created therewith. In another aspect, a tapered surface adjacent a distal end of a clinching punch has an angle of 20-35 degrees relative to a distal end. A further aspect of a clinching apparatus provides a tapered surface adjacent a distal end which is configured in accordance with a specific formula. Additional advantages and features of the present clinching apparatus can be ascertained from the following description and appended claims taken in conjunction with the present drawings.